2 Top Performance Areas

This chapter describes the top tuning areas for Oracle Fusion Middleware. It covers critical Oracle Fusion Middleware performance areas and provides a quick start for tuning Java applications in the following sections:

2.1 Identifying Top Performance Areas

One of the most challenging aspects of performance tuning is knowing where to begin. This chapter serves as a 'quick start' guide to performance tuning your Oracle Fusion Middleware applications.

Table 2-1 provides a list of common performance considerations for Oracle Fusion Middleware. While the list is a useful tool in starting your performance tuning, it is not meant to be comprehensive list of areas to tune. You must monitor and track specific performance issues within your application to understand where tuning can improve performance. See Chapter 4, "Monitoring Oracle Fusion Middleware" for more information.

Logging levels are thresholds that a system administrator sets to control how much information is logged. Performance can be impacted by the amount of information that applications log therefore it is important to set the logging levels appropriately.

2.2 Securing Sufficient Hardware Resources

A key component of managing the performance of Oracle Fusion Middleware applications is to ensure that there are sufficient CPU, memory, and network resources to support the user and application requirements for your installation.

No matter how well you tune your applications, if you do not have the appropriate hardware resources, your applications cannot reach optimal performance levels. Oracle Fusion Middleware has minimum hardware requirements for its applications and database tier. For details on Oracle Fusion Middleware supported configurations, see "System Requirements and Prerequisites" in Planning an Installation of Oracle Fusion Middleware.

Sufficient hardware resources should meet or exceed the acceptable response times and throughputs for applications without becoming saturated. To verify that you have sufficient hardware resources, you should monitor resource utilization over an extended period to determine if (or when) you have occasional peaks of usage or whether a resource is consistently saturated. For more information on monitoring, see Chapter 4, "Monitoring Oracle Fusion Middleware".

Tip:

Your target CPU usage should never reach 100% utilization. You should determine a target CPU utilization based on your application needs, including CPU cycles for peak usage.

If your CPU utilization is optimized at 100% during normal load hours, you have no capacity to handle a peak load. In applications that are latency sensitive and maintaining a fast response time is important, high CPU usage (approaching 100% utilization) can increase response times while throughput stays constant or even decreases. For such applications, a 70% - 80% CPU utilization is recommended. A good target for non-latency sensitive applications is about 90%.

If any of the hardware resources are saturated (consistently at or near 100% utilization), one or more of the following conditions may exist:

The hardware resources are insufficient to run the application.

The system is not properly configured.

The application or database must be tuned.

For a consistently saturated resource, the solutions are to reduce load or increase resources. For peak traffic periods when the increased response time is not acceptable, consider increasing resources or determine if there is traffic that can be rescheduled to reduce the peak load, such as scheduling batch or background operations during slower periods.

Oracle Fusion Middleware provides a variety of mechanisms to help you control resource concurrency; this can limit the impact of bursts of traffic. However, for a consistently saturated system, these mechanisms should be viewed as temporary solutions. For more information see Section 2.9, "Controlling Concurrency".

2.3 Tuning the Operating System

Each operating system has native tools and utilities that can be useful for monitoring and tuning purposes. Native operating system commands enable you to monitor CPU utilization, paging activity, swapping, and other system activity information.

For details on operating system commands, and guidelines for performance tuning of the network or operating system, refer to the documentation provided by the operating system vendor.

2.5 Tuning the WebLogic Server

If your Oracle Fusion Middleware applications are using the WebLogic Server, see "Tuning WebLogic Server" in Tuning Performance of Oracle WebLogic Server.

2.6 Tuning Database Parameters

To achieve optimal performance for applications that use the Oracle database, the database tables you access must be designed with performance in mind. Monitoring and tuning the database ensures that you get the best performance from your applications.

Note:

The information in this section is a subset of database tuning information for Fusion Middleware. More information can be found in Oracle Database Performance Tuning Guide. Make sure that you have also reviewed your database tuning documentation.

2.6.1 Tuning Database Parameters

The following tables provide common init.ora parameters and their descriptions. Consider following these guidelines to set the database parameters. Ultimately, however, the DBA should monitor the database health and tune parameters based on the need. See Table 2-2 for more information:

Table 2-2 Important inti.ora Oracle 11g Database Tuning Parameters

Database Parameter

Description

AUDIT_TRAIL

If there is NO policy to audit db activity, consider setting this parameter to NONE. Enabling auditing can impact performance.

MEMORY_MAX_TARGET

MEMORY_MAX_TARGET specifies the maximum value to which a DBA can set the MEMORY_TARGET initialization parameter.

MEMORY_TARGET

Consider setting the MEMORY_TARGET to NONE. Set SGA and PGA separately as setting MEMORY_TARGET does not allocate sufficient memory to SGA and PGA as needed.

PGA_AGGREGATE_TARGET

Consider using a value of 1G for PGA initially and then monitor the production database on daily basis and adjust SGA and PGA accordingly.

If the database server has more memory, consider setting PGA_AGGREGATE_TARGET to a value higher than 1G based on usage needs.

Consider using a value of 2G for SGA is 2G to start with and initially and then monitor the production database on daily basis and adjust SGA and PGA accordingly.

If the database server has more memory, consider setting SGA_TARGET to a value higher than 2G based on usage needs.

2.6.2 Tuning Redo Logs Location and Sizing

Tuning the redo log options can provide performance improvement for applications running in an Oracle Fusion Middleware environment, and in some cases, you can significantly improve I/O throughput by moving the redo logs to a separate disk.

Consider having at least 3 redo log groups with 2G of size each. Redo log files should be placed on a disk separate from data files to improve I/O performance.

2.6.3 Tuning Automatic Segment-Space Management (ASSM)

For permanent tablespaces, consider using automatic segment-space management. Such tablespaces, often referred to as bitmap tablespaces, are locally managed tablespaces with bitmap segment space management.

For backward compatibility, the default local tablespace segment-space management mode is MANUAL.

While configuring tablespaces, consider setting the extent allocation type to SYSTEM. If the allocation type is set to UNIFORM, it might impact performance.

2.7 Reusing Database Connections

Creating a database connection is a relatively resource intensive process in any environment. Typically, a connection pool starts with a small number of connections. As client demand for more connections grow, there may not be enough in the pool to satisfy the requests. WebLogic Server creates additional connections and adds them to the pool until the maximum pool size is reached.

One way to avoid connection creation delays is to initialize all connections at server startup, rather than on-demand as clients need them. This may be appropriate if your load is predictable and even. Set the initial number of connections equal to the maximum number of connections in the Connection Pool tab of your data source configuration. Determine the optimal value for the Maximum Capacity as part of your pre-production performance testing.

If your load is uneven, and has a much higher number of connections at peak load than at typical load, consider setting the initial number of connections equal to your typical load. In addition, consider setting the maximum number of connections based on your supported peak load. With these configurations, WebLogic server can free up some connections when they are not used for a period of time.

2.8 Enabling Data Source Statement Caching

When you use a prepared statement or callable statement in an application or EJB, there may be a performance impact associated with the processing of the communication between the application server and the database server and on the database server. To minimize the processing impact, enable the data source to cache prepared and callable statements used in your applications. When an application or EJB calls any of the statements stored in the cache, the server reuses the statement stored in the cache. Reusing prepared and callable statements reduces CPU usage on the database server, improving performance for the current statement and leaving CPU cycles for other tasks.

Each connection in a data source has its own individual cache of prepared and callable statements used on the connection. However, you configure statement cache options per data source. That is, the statement cache for each connection in a data source uses the statement cache options specified for the data source, but each connection caches it's own statements. Statement cache configuration options include:

Statement Cache Type—The algorithm that determines which statements to store in the statement cache.

Statement Cache Size—The number of statements to store in the cache for each connection. The default value is 10. You should analyze your database's statement parse metrics to size the statement cache sufficiently for the number of statements you have in your application.

You can use the Administration Console to set statement cache options for a data source. See "Configure the statement cache for a JDBC data source" in the Oracle WebLogic Server Administration Console Online Help.

2.9 Controlling Concurrency

Limiting concurrency, at multiple layers of the system to match specific usage needs, can greatly improve performance. This section discusses a few of the areas within Oracle Fusion Middleware where concurrency can be controlled.

When system capacity is reached, and a web server or application server continues to accept requests, application performance and stability can deteriorate. There are several places within Oracle Fusion Middleware where you can throttle the requests to avoid overloading the mid-tier or database tier systems and tune for best performance.

2.9.1 Setting Server Connection Limits

Oracle HTTP Server uses directives in httpd.conf. This configuration file specifies the maximum number of HTTP requests that can be processed simultaneously, logging details, and certain limits and time outs.

You can use the MaxClients and ThreadsPerChild directives to limit incoming requests to WebLogic instances from the Oracle HTTP Server based on your expected client load and system resources. The following sections describe some Oracle HTTP Server tuning parameters related to connection limits that you typically need to tune based on your expected client load. See Chapter 6, "Oracle HTTP Server Performance Tuning" for more information and a more complete list of tunable parameters.

2.9.1.1 MaxClients/ThreadsPerChild

Note:

The MaxClients parameter is applicable only to UNIX platforms and on Microsoft Windows (mpm_winnt), the same is achieved through the ThreadsPerChild and ThreadLimit parameters.

The MaxClients property specifies a limit on the total number of server threads running, that is, a limit on the number of clients who can simultaneously connect. If the number of client connections reaches this limit, then subsequent requests are queued in the TCP/IP system up to the limit specified (in the ListenBackLog directive).

You can configure the MaxClients directive in the httpd.conf file up to a maximum of 8K (the default value is 150). If your system is not resource-saturated and you have a user population of more than 150 concurrent HTTP connections, you can improve your performance by increasing MaxClients to increase server concurrency. Increase MaxClients until your system becomes fully utilized (85% is a good threshold).

When system resources are saturated, increasing MaxClients does not improve performance. In this case, the MaxClients value could be reduced as a throttle on the number of concurrent requests on the server.

If the server handles persistent connections, then it may require sufficient concurrent httpd server processes to handle both active and idle connections. When you specify MaxClients to act as a throttle for system concurrency, you need to consider that persistent idle httpd connections also consume httpd processes. Specifically, the number of connections includes the currently active persistent and non-persistent connections and the idle persistent connections. When there are no httpd server threads available, connection requests are queued in the TCP/IP system until a thread becomes available, and eventually clients terminate connections.

You can define a number of server processes and the threads per process (ThreadsPerChild) to handle the incoming connections to Oracle HTTP Server. The ThreadsPerChild property specifies the upper limit on the number of threads that can be created under a server (child) process.

Note:

ThreadsPerChild, StartServers, and ServerLimit properties are inter-related with the MaxClients setting. All of these properties must be set appropriately to achieve the number of connections as specified by MaxClients. See Table 6-1, "Oracle HTTP Server Configuration Properties" for a description of all the HTTP configuration properties.

2.9.1.2 KeepAlive

A persistent, KeepAlive, HTTP connection consumes an httpd child process, or thread, for the duration of the connection, even if no requests are currently being processed for the connection.

If you have sufficient capacity, KeepAlive should be enabled; using persistent connections improves performance and prevents wasting CPU resources re-establishing HTTP connections. Normally, you should not need to change KeepAlive parameters.

Note:

The default maximum requests for a persistent connection is 100, as specified with the MaxKeepAliveRequests directive in httpd.conf. By default, the server waits for 15 seconds between requests from a client before closing a connection, as specified with the KeepAliveTimeout directive in httpd.conf.

2.9.1.3 Tuning HTTP Server Modules

The Oracle HTTP Server (OHS) uses the mod_wl_ohs module to route requests to the underlying Weblogic server or the Weblogic Server cluster. The configuration details for mod_wl_ohs are available in the mod_wl_ohs.conf file in the config directory.

2.9.2 Configuring Connection Pools

Connection pooling is configured and maintained per Java runtime. Connections are not shared across different runtimes. To use connection pooling, no configuration is required. Configuration is necessary only if you want to customize how pooling is done, such as to control the size of the pools and which types of connections are pooled.

You configure connection pooling by using a number of system properties at program startup time. Note that these are system properties, not environment properties and that they affect all connection pooling requests.

For applications that use a database, performance can improve when the connection pool associated with a data source limits the number of connections. You can use the MaxCapacity attribute to limit the database requests from Oracle Application Server so that incoming requests do not saturate the database, or to limit the database requests so that the database access does not overload the Oracle Application Server-tier resource.

The connection pool MaxCapacity attribute specifies the maximum number of connections that a connection pool allows. By default, the value of MaxCapacity is set to 15. For best performance, you should specify a value for MaxCapacity that matches the number appropriate to your database performance characteristics.

Limiting the total number of open database connections to a number your database can handle is an important tuning consideration. You should check to make sure that your database is configured to allow at least as large a number of open connections as the total of the values specified for all the data sources MaxCapacity option, as specified in all the applications that access the database.

2.9.3 Tuning the WebLogic Sever Thread Pool

By default WebLogic Server uses a single thread pool, in which all types of work are executed. WebLogic Server uses Work Managers to prioritize work based on rules you can define, and run-time metrics, including the actual time it takes to execute a request and the rate at which requests are entering and leaving the pool. There is a default work manager that manages the common thread pool.

The common thread pool changes its size automatically to maximize throughput. WebLogic Server monitors throughput over time and based on history, determines whether to adjust the thread count. For example, if historical throughput statistics indicate that a higher thread count increased throughput, WebLogic increases the thread count. Similarly, if statistics indicate that fewer threads did not reduce throughput, WebLogic decreases the thread count.

Since the WebLogic Server thread pool by default is sized automatically, in most situations you do not need to tune this. However, for special requirements, an administrator can configure custom Work Managers to manage the thread pool at a more granular level for sets of requests that have similar performance, availability, or reliability requirements. With custom work managers, you can define priorities and guidelines for how to assign pending work (including specifying a min threads or max threads constraint, or a constraint on the total number of requests that can be queued or executing before WebLogic Server begins rejecting requests).

Use the following guidelines to help you determine when to use Work Managers to customize thread management:

The default fair share is not sufficient.

This usually occurs in situations where one application needs to be given a higher priority over another.

A response time goal is required.

A minimum thread constraint needs to be specified to avoid server deadlock.

You use MDBs in your application.

To ensure MDBs use a well-defined share of server thread resources, and to tune MDB concurrency, most MDBs should be modified to reference a custom work manager that has a max-threads-constraint. In general, a custom work manager is useful when you have multiple MDB deployments, or if you determine that a particular MDB needs more threads.

See Also:

For more information on how to use custom Work Managers to customize thread management, and when to use custom work managers, see the following:

You can use Oracle WebLogic Administration Console to view general information about the status of the thread pool (such as active thread count, total thread count, and queue length.) You can also use the Console to view each application's scoped work manager metrics from the Workload tab on the Monitoring page. The metrics provided include the number of pending requests and number of completed requests.

For more information, see "Servers: Monitoring: Threads" and "Deployments: Monitoring: Workload" in the Oracle WebLogic Server Administration Console Online Help.

The work manager and thread pool metrics can also be viewed from the Oracle Fusion Middleware Control.

2.10 Setting Logging Levels

The amount of information that applications log depends on how the environment is configured and how the application code is instrumented. To maximize performance it is recommended that the logging level is not set higher than the default INFO level logging. If the logging setting does not match the default level, reset the logging level to the default for best performance.

Once the application and server logging levels are set appropriately, ensure that the debugging properties or other application level debugging flags are also set to appropriate levels or disabled. To avoid performance impacts, do not set log levels to levels that produce more diagnostic messages, including the FINE or TRACE levels.

Each component may have specific recommendations for logging levels. See the component chapters in this book for more information.

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